Helianthemum nummularium aka Common Rock Rose

Helianthemum nummularium is known as rock rose or sun rose. It belongs to the Cistaceae family. This small evergreen shrub grows low and spreads across the ground. Sources place its range in Europe and southwest Asia. The RHS also records it as native to Britain and Ireland. It grows in grassland and scrub on basic soils.

Garden plants reach about 0.5–1 foot (0.15–0.3 m) tall. Their creeping stems can spread to 3 feet (0.91 m). RHS size bands allow heights up to 1.6 feet (0.5 m). Its account gives a smaller spread than Missouri Botanical Garden. Woody stems carry grey-green leaves that remain through winter. Leaf shape varies between the accounts, from small ovals to narrow, lance-shaped blades. The low growth makes a leafy mat rather than an upright bush.

Flowers appear from late spring into summer, often during May and June. Each bloom has five petals and reaches about an inch across. Yellow is the main colour, though pink blooms also occur. Flowers grow in clusters at the stem tips. Each lasts just one day, but fresh blooms extend the show. In good conditions, flowers can hide much of the foliage. Their open, shallow shape gives them a small rose-like look.

Grow this plant in full sun with soil that drains well. Missouri Botanical Garden favours dry, rocky or sandy loam. RHS also accepts moist soil where excess water drains away. Neutral to alkaline soil suits it, though it tolerates acid soil. It withstands drought, but wet soil can cause rot. Missouri Botanical Garden lists USDA zones 6–8; Chicago lists 5–7. Survival in zone 5 can be uncertain, so winter cover may help. RHS rates its UK hardiness as H5. Cool summers and mild winters suit it better than harsher seasonal swings.

Use rock rose in rock gardens, borders, or as ground cover. Its stems can trail over walls and cover dry slopes. Trim plants after flowering to keep their shape and prompt new growth. Sow seed in autumn, or take softwood cuttings in late spring or early summer. Pests rarely cause trouble, and serious disease problems are uncommon. Honey fungus may pose a risk where it already occurs. The degree of risk remains unclear. Plants For A Future lists no known edible uses or hazards. It records use in Bach flower preparations, not evidence of medical benefit.